Hubble Ultra Deep Field

Staff: Mentor

Astronomers at the Space Telescope Science Institute today unveiled the deepest portrait of the visible universe ever achieved by humankind. Called the Hubble Ultra Deep Field (HUDF), the million-second-long exposure reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the big bang when the first stars reheated the cold, dark universe. The new image should offer new insights into what types of objects reheated the universe long ago.

Supposedly the now famous original Hubble Deep Field covered an area of sky equivalent to the size of a grain of sand held at arms distance. How small an area does this new Ultra Deep Field photo cover?

I recently saw a documentary on Discovery covering the Hubble telescope. At the very end of the program they said something about the next-generation Hubble, which (if they get the thing up somehow... $-wise) will be positioned 1 000 000 kms from earth.
Sounds good! They want to look at the universe at an even earlier stage. Pictures like the one posted above make us feel good about such projects again.

Staff: Mentor

Originally posted by Loren Booda The Hubble Deep Field had been my favorite wallpaper. Thanks for helping me redesign my space with the HUDF.

I'm alrady planning the poster/collage I'm going to make of it. I'll take a large photo of the whole thing for the center and two small blowups of individual galaxies or portions of it to each side/top/bottom.

Supposedly the now famous original Hubble Deep Field covered an area of sky equivalent to the size of a grain of sand held at arms distance. How small an area does this new Ultra Deep Field photo cover?

-HUDF covers a field of about 1/10 the diameter of the Moon, or
roughly 1/13millionth of the sky.
-HUDF contains about 10,000 galaxies.
-The oldest objects in HUDF formed roughly 800 million
years after the Big Bang.
-Hubble recieved roughly 1 photon per minute from the more
distant objects in HUDF.
-The total exposure length was roughly 11 days.

Amazing! and if one looks close, actually if one moves away from the full image to about 6ft, one can clearly see an 'S'(rotation to the left of 12:00 clock), barred shape collection of Galaxies, almost as if flying outwards from a catherine wheel firework!

Just a quick clarification: the picture shows what the universe may have looked like billions of years ago because of the speed of light and the distance it has to travel to get to the hubble camera? So in essence, the other galaxies may be more developed now, but they don't appear so to us yet... sound right?

From the press release: "The ACS uncovered galaxies that existed 800 million years after the big bang (at a redshift of 7). But the NICMOS may have spotted galaxies that lived just 400 million years after the birth of the cosmos (at a redshift of 12). Thompson must confirm the NICMOS discovery with follow-up research."

Here is an example of how this kind of follow-up has been done using large Earth-based telescopes. While the objects that Gemini looked at are not in the UDF (they're very close near by), and as the faint galaxies have already been located (on NICMOS images) the 'search' part of the GEMINI work is already done, the spectra will likely be obtained in a manner similar to that described in the link.

Originally posted by Embermage Just a quick clarification: the picture shows what the universe may have looked like billions of years ago because of the speed of light and the distance it has to travel to get to the hubble camera? So in essence, the other galaxies may be more developed now, but they don't appear so to us yet... sound right?

Not quite.

a) the distant galaxies are much redder in the image than they would have looked if you had been there at the time

b) the image contains objects at distances from 'next door' (e.g. stars in our own Milky Way), through 'sort of close' (e.g. galaxies 'only' ~1 billion light years distant), to extremely distant galaxies. In the early days of the universe, if you were there, you'd also see nearby stars and quite a few nearby 'galaxies' (they'd look quite different), but no distant ones.

You are right in saying that we're seeing the galaxies as they were when the light we now record left the galaxies, ~ 1 billion to ~<13 billion years ago. IF we could 'see' them 'today', they'd look different (the 'nearby' ones would look similar to how they appear in the image; the distant ones, likely very different).

Staff: Mentor

Originally posted by Dagenais That sucks though. Having to wait for new discoveries, as opposed to sciences like Computers, where you don't have to wait a certain amount of time for new, important discoveries.

With 10,000 galaxies in that photo alone (remember, not all of them are 13 billion light years away - many are much closer), waiting for the light to get here is not a concern.

Originally posted by Dagenais That sucks though. Having to wait for new discoveries, as opposed to sciences like Computers, where you don't have to wait a certain amount of time for new, important discoveries.

'Twas ever thus in astronomy Dagenais, whether the Crab Nebula, a supernova recorded by Chinese, Korean (and more) folk nearly 1,000 years ago, but which exploded some 6,500 years earlier; or SN1987 in the Larger Magellenic Cloud (which many PF members probably saw with their own eyes in 1987), but which exploded some ~165,000 years earlier; or GRB030329, one of the brightest and nearest gamma ray bursts observed to date, on 29 March 2003 (and Finnish amateur astonomers' observations of which contributed to confirming the GRB-supernova connection), but which originated over 2 billion years ago.

The black body radiation is an artifact of the epoch of decoupling (~400,000 years), when hydrogen became largely un-ionized. This hydrogen condensed to form stars (~80,000,000 years), which in turn formed galaxies (<1,000,000,000 years).

Condensation of hydrogen takes place where the Jeans radius, limited by the mean free path of sound in the medium under gravity and at a given temperature, determines the expanse of gaseous agglomeration.

If this view touches the very edge of the "Dark Ages", when recombination made electrons join up with nuclei, is there light (EM radiation) to be expected at an earlier time than this? Are there only neutrino and gravitational radiation to be expected from before this time?